Effects of aging and antioxidants on glucose transport in rat adipocytes

The free radical theory of aging postulates that free radicals are the underlying cause of aging. One of the well-established age-associated disorders is the decrease in the insulin-stimulated glucose transport through the cell membrane which was reported to be a major mechanism underlying insulin resistance in old rats. The present study investigates the protective capacity of two known antioxidants, vitamin C and butylated hydroxytoluene (BHT), against age-associated free radical damage, which could be the reason behind the decreased insulin-stimulated glucose transport in old animals. Maximum insulin-stimulated glucose transport has been estimated in adipocytes isolated from adult 6-month-old Fischer rats and from senile 24-month-old control rats as well as from 24-month-old rats that were fed either vitamin C or BHT for 18 months. A significant increase in maximum insulin-stimulated glucose transport was observed in the BHT (p = 0.015) and the vitamin C groups (p = 0.039) compared with the control group of the same age. Significant stimulations with insulin over basal activities were also observed in the BHT group (p = 0.0001) as well as the vitamin C group (p = 0.009), while a nonsignificant stimulation (p = 0.097) was observed in the old control group. This study suggests a protective role that BHT (fat soluble) may have on the lipid moiety of the cell membrane and vitamin C (water soluble) on one or more of the intracellular cytoplasmic constituents concerned with glucose transport.